Modified v-bottom boat



Dec. 1, 1959 H. JOHNSTON MODIFIED V-BOTTOM BOAT s sham-sheet 1 Filed April 29. 1955 INVENT OR Lasua HJOHNSTON ATTORNEYS.

Dec. 1, 1959 L. H. JOHNSTON 2,915,031

MODIFIED V-BOTTOM BOAT Filed April 29. 1955 5 Sheets-Sheet 2 INVENTOR LESLIE. H. JOHNS O VBY MW l-B ATTORNEYS MODIFIED V BOTTOM BOAT Filed April 29. 1955 3 Sheets-Sheet 3 1 I -----1--- I as INVENTOR LESLIE HJoHNsToN BY Z9 ATTORNEYS United States Patent 2,915,031 MODIFIED V-BO'ITOM BOAT Leslie H. Johnston, New Orleans, La. Application April 29, 1955, Serial No; 504,975 6 Claims. (Cl. 114-56 This inventionrelates to boat hulls of the hard chines type provided with a concave V-bottom and aims to pro-' vide such a hull of maximum stability, both lateral'-and-..-:

longitudinal, better than average speed, large carrying' capacity, and safety under all conditions of w1nd-.and'sea-;= Further specific objects of the invention are -to Prevent pounding in a rough sea, to hold a true course without.-

wandering, andto prevent undue banking when putoven hard at full speed.

Other. aims and advantages of the invention-appear- 1 in connection with the following description of a pre ferred form 'of hull as shown in the accompanying draw ings, wherein:

Figure 1* is a bottom plan showing the outline of thew deck and chine line;

Figure 2 is a :side elevation; and Figure .3 is a front elevation of the boat, Figs -1, 2 and 3 being drawn to the same scale;

Figures 4, -5, 6, 7 and S-are transverse outlines of the bottom portion of the hull on cross-section-planes des1gnated by the lines 4-4, 55, 6 6, 7-7 and 88,'

respectively, in Figures land 2; andw Figure -9 shows an outline of the template 11Sed-ll1 determining the curvature of the concave bottom of the hull, Figs. 4 to 9, inclusive being drawn to a larger scale than Figs. l, 2 and 3.

In the illustrative boatthe engines, propellers, rudder and other accessories are not shown as the invention pertains to the hull and any suitable propelling machinery maybe installed to suit' the desired speed and workingconditions, running speeds up to 30 miles per hour for working boats and higher top speeds for pleasure boats being. readily obtainable.

Referring to the drawings, the hull has. a concave V-bottom comprising flat marginal sections 10 'whichmerge into concave sections 1 1 converging at the line of the keel and bordered bystraight side walls12, the fore part having a deck 13 and the.afterIpart'being open and partly covered by a cabin type roof 14; The chine -line.

15 (see ,Fig. 1) where the bottom and side walls meet in an obtuse angle is parallel to the waterline strip 16in the after part of the hull, and crossesthewaterlinezand emerges near the bow, the greatest width of the bottom: a being considerably aft of amidships, and the beam being r greatest aft of amidships, the deck line 17 being widest forward of amidships and tapering aft to a narrower width than the chine line at the stern. i

The stem 18 is almost straight up andvd'own andslightly bowed outwardsfromone. side ,of the hull to the other. The prow at the'deck line is, quite full and the stem 19 is nearly vertical and curves sharplyjust below the waterline where itsmerges intothe keel line 20 under the concave V-bottom which is characteristic of the fore part of the hull.

The shape of the hull transversely at typical points along its longitudinal axis is shown in Fig. 3, wherein the outlines 21, 22 and 23 indicate clearly the crosssectional shape of the vertical planes through the lines ice 44,5-5 and. 6+6, respectively; in Figures 1 and-2.

the after partof the hull.

jacent to the keel line with the flat sections 10 on'eachside thereof,

The shape of the bottom is designed to the desired concave formby means of a reversible template 25'made: in accordancewithmy invention, as illustrated in Figure 9, wherein the-dimensions -of the master .curve are suitable for a boat-from-40 feet to 50 feet in length. Smaller and larger boats may be designed accordingwto l thesame system, theJmaster'curve being modified to maintain the proportions about the same as in that's illustrated.-- r

In theform of invention illustrated, thetemplate 25 has a longstraight section over 6 feet in length terminat-- Fatentetlv Decal 1 959. I.

ing in a smooth curve having an initial portion of 6 feet radius of gradually increasing sharpness passing through points; 26, 27 and28, on the radii-at 22 /z intervals,

through the. center of curvature of the 6 footportion and a rlistantfrom saidcenter 6 feet, 5 ft. 10 /2 in. and 5 ft. 6 in'.; respectively, terminating at a point 29 on the radius from-the pointof departure and at a distance, of 5 ft. l /zin. from said 'center. For a55 foot hull the'se dimen-i I sionsmaybe increased by about four inches. In order to determine the shape of tliehullbottomat successive frames of the structure, the horizontal :plan outlineof the chines islaid-out as shownin Fig;' 1 with 3.. the beam at the stern about equal to thatamidshipsp and tapering to a point at the stem, the after portion". having a slightly greater beam than the stern transom and amidships frames so that the maximum beam at the chines is located about one-fourthyof the length of the hull. forward from the stern, and the chinelinesain plan.

curve outwards for the entire length. of the hull, the I curvaturev being somewhat sharper approaching the bow than throughout the after part of the hull where the chine line is only slightly convex.

Looking at the side of the hull, the chine and the. Waterlineaarenparallelfor nearly the entire length of the '1 after halft of the hull, andsthe chinerises towardthe. prow so as to crossithe waterline near the prow; The keel .line hasits greatest depth forward of the middlethird of therlengthtof thehull, in the illustrative boat it being at a point about one-fifth of thelength of the boat back from .the bow end of the hull, where it is. about 3 ft. 6 in. below thewaterline and'about2 ft. 8 or 9 in.

below" the chine From this point the "keelrline rise's; toward the-. prow in a smooth curvento merge into the, I stem at just abouttheWaterlinew-The keelline becomes less and less: deep all the way from its maximum depth to the reartransom where itextends about-6 in. below the-.

almost flat bottom of the hull.

In order .to determine the shaped the hull bottom at each frame throughout the after four-fifths of the length of the hull, the curvature isobtained by laying the template 25 on an outline-or profile of the transverse section of the hull at the framein questionwwith-its straight section on c a liner withi'the chine to establislnthe flat part of the bottom and its curved portiontintersecting" the mid 'pl'anez of symmetry at the line of the keel, and then drawing in-the curved or concave portion of the bottom. By shifting the template laterally towards the keel line a little further at each frame from bow to stern, the result will be a gradual widening of the fiat bottom and no fairing of the design will be required to provide a smooth transition from the concaveto the fiat surfaces.

The first'few frames have no flat horizontal surfaces and may be shaped in accordance with Figure 4 to give a somewhat fiatter curvature near the bow than would result from laying the straight section of the template on the frame section profile exactly parallel with the horizontal, depending on the amount of fullness desired at the bow, while providing smooth fairing at all submerged areas of the bottom. The shape and dimensions of the hull bottom below the chines are calculated'to afiord a lowvcenter of displacement well aft of amidships, the fore body being sharp both longitudinally and vertically where it meets the water when moving fast through cross seas, thus allowing an easy entrance into the seas and avoiding pounding near the bow, while maintaining good lateral stability. As the bow descends into a sea, the buoyancy increases rapidly because of the concave shape of the forward part of the hull bottom, thus checking the pitching action gradually while preventing nose diving, and maintaining the planing attitude of the large flat planing surfaces on each side of the keel that start well forward of amidships, thereby avoiding loss of speed and lift.

My design of hull possesses the lateral stability characteristic of hard chine boats, which is accentuated by high speed beacuse of the equal distribution of the wide planing areas below the waterline well aft on each side of the keel line where the entire bottom is constantly in contact with the water. At the same time, due to the concave shape of the forward part of the bottom, only a small portion of the hull is submerged, the greater part of the water displaced passing astern under the bottom because of the smooth fairing near the bow, and directional stability is maintained by the full length keel.

No deadwood, bilge keels, oversize rudder or other device for maintaining directional or lateral stability is required with my design, but the propellers may be protected with skegs without interfering with the riding qualities of the hull.

Tests of boats constructed according to my design made at full speed with full load indicate that shifting of the load has little effect on the lateral equilibrium and stability of the hull, as the center of lateral buoyancy shifts significantly. laterally with a slight change in the angle of equilibrium, thereby minimizing both roll and banking. Even in rough water the hull has less resistance and is more comfortable at full speed than other comparable designs heretofore in use.

Other advantages of my invention are good directional stability, i.e., ability to hold a course in all kinds of wind and sea without wandering; short turning radius at full speed; moderate lifting at the bow and'squatting at the stern 'at'full speed; comparatively low fuel consumption; and ability to maneuver in any direction at any time an at any speed with complete safety.

These advantages I believe are inherent in the hull design resulting from my system of laying out the bottom by means of the master pattern 25; but my invention is not restricted to such a system, as it includes displacement type hull designs produced by other means embodying the characteristic features claimed having minimum surface area in contact with the water at high speeds, maximum planing surface at optimum attitude in rough water, and adequate keel area for stability and control under all weather and wave conditions, making for safety and comfort both light and loaded at sea and in protected waters; and no claim is made herein to the use of a template of the character described apart from its function as a convenient means of identifying the claimed shape of hull bottom.

I claim the following as my invention: 1. A boat hull of the modified flat bottom hard chine type having a V-shaped hull bottom portion coaxial with the center line of the hull, a stern transom and an overhanging sharp prow suitable for rough water at full speed, said hull being characterized by the after part of its bottom being substantially flat and the fore part being fully concave from hull center line to chines, the intermediate part of the bottom being fiat at its outer edges and concave near said center line, with the fiat areas increasing in width throughout their length from fore to aft and the inner margins thereof extending downwards in conformity to decreasing widths of similar curved surfaces and converging to form the V-shaped hull bottom portion for the greater part of its length.

2. A boat hull as set forth in claim 1 wherein the transverse shape of the bottom amidships is flat horizontally from the chines inwards approximately one-third of the distance to the hull center line and curves downwards to form a V at the keel line having an interior angle of about 3. A boat hull as set forth in claim 1 wherein the beam at the chines has its maxi-mum width aft of amidships.

4. A boat hull as set forth in claim 1 wherein the beam at the chines is the same at the transom as amidships.

5. A boat hull of the modified flat bottom hard chine type having a concave V-shaped central portion extending the full length of the bottom below the chines and merging into an overhanging prow at the bow, the included angle between the downwardly converging sides of said central portion being approximately 90 at the keel line at an intermediate part of its length, said angle increasing towards the stern and decreasing towards the bow, and the depth of the concave V-shaped central portion increasing towards the bow and decreasing towards the stern, the greatest depth being forward of the middle third of the length of the hull, the bottom portions on each side of said central portion being flat for at least the aft two thirds of their length and lying in parallel planes at approximately the same depth below the waterline for the greater part of the length of the hull, said bottom portions increasing in width progressively towards the stern and merging tangentially with said central portion along their entire lengths, thereby forming two substantially fiat bottom areas extending aft one on each side of' said central portion for over half the length of the hull and progressively wider from their origin forward of the middle third of the length of the hull to the stern transom, whereby said hull exhibits good maneuverability and stability at high speed in rough water.

6. A boat hull as set forth in claim 5 wherein the greatest width of beam at the chines is aft of the mid-length of the hull.

References Cited in the file of this patent 29, published in 1941 by Cornell Press, New York. 

